The present invention relates generally to heating appliances, such as toasters or toaster ovens, and more specifically to a switch mechanism for such appliances"" bread support.
In heating appliances, such as toasters and toaster ovens, a food item is placed on a bread support that supports the food item as it is lowered into and removed from a bread cavity of the appliance. FIG. 1 is an isometric view of a conventional toaster 10 with its external housing (not shown) removed to better illustrate the internal components of the toaster 10. The toaster 10 includes a shell 14 formed from two side panels 16, 17, two end panels 18, 20, and a bottom 22 that are secured to each other by suitable means. An outer bread guard 26 is positioned inside the side panel 16 and an identical outer bread guard 28 is positioned inside the side panel 17. Two inner bread guards 32 and 34 are also positioned between the outer guards 26 and 28. Each of the bread guards 26xe2x80x9434 includes a horizontal member 36 and vertical members 38. A first bread cavity 40 is defined between the bread guards 26 and 32, and a second bread cavity 42 is defined between the bread guards 28 and 34. The bread guards 26-34 function to protect bread placed between the bread guards from heating elements (not shown in FIG. 1) positioned inside the side panels 16 and 17 as well as between the center bread guards 32 and 34.
A first bread support (not shown) is contained within the first bread cavity 40 and functions to support a piece of bread as it is lowered into and raised from the bread cavity 40. A second bread support (not shown) is similarly positioned within the second bread cavity 42 to support another piece of bread in the bread cavity 42. Each of the bread supports includes a lever 46, 48 extending through respective slots 50 and 52 in the end panel 18. The levers 46, 48 are coupled to respective slides 56, 58 that slide on respective vertically oriented rods 60, 62. The slides 56, 58 are straddled by respective brackets 74, 76 that also slide along the respective rods 60, 62. The brackets 74, 76 are coupled to an actuating handle 78 positioned outside the housing (not shown). The toaster 10 further includes an edge panel 80 positioned at the bottom of the end panel 18. A switch mechanism and retainer 82 is mounted on the edge panel 80.
In operation, the actuating handle 78 is pushed down to cause the brackets 74, 76 to slide downwardly on the respective rods 60, 62. As the brackets 74, 76 slide downwardly, they perform two functions. First, the brackets 74, 76 allow their respective slides 56, 58 to move downwardly until they contact respective stops (not shown in FIG. 1). The slides 56, 58 allow the levers 46, 48 to move downwardly to lower the bread on the bread supports in the bread cavities 40, 42. As the levers 46, 48 are pushed down, the outer bread guards 26, 28 move toward the center of the corresponding bread cavity 40, 42, as shown for the bread guard 28. In this way, the bread guards 26-34 position the bread in approximately the centers of the bread cavities 40 and 42 so that the bread placed on the bread supports is not positioned too close to the heating elements.
Second, when the brackets 74, 76 reach their lower positions, they actuate a switch (not shown) in the switch mechanism and retainer 82 to apply power to the heating elements of the toaster 10 during a heating cycle. The brackets 74, 76 are held in their lowered position during the heating cycle by an electromagnet (not shown) in the switch mechanism and retainer 82. At the end of the heating cycle, the electromagnet releases the brackets 74, 76, thereby allowing the brackets 74, 76 to be pulled upwardly by a spring (not shown in FIG. 1) extending between the brackets 74, 76 and a fixed location on the toaster 10. As the brackets 74, 76 move up, they raise the slides 56, 58, respectively, which, in turn, raise the respective levers 46, 48 thereby raising the bread supports in the bread cavities 40, 42, respectively. Although the switch mechanism and retainer 82 is described as controlling the toasting time, one skilled in the art will realize that other mechanisms such as a mechanical heat sensing mechanism may also be utilized.
FIGS. 2A-2C are schematic diagrams showing one of the brackets 74 and associated components to illustrate the operation of the toaster 10 bread support. Referring to FIG. 2A, the bread support bracket 74 includes a top leg 92, a side leg 94 and a bottom leg 96. The top leg 92 and the bottom leg 96 are formed to slide along the rod 60. A spring 98 is connected between one of the legs 92-96 and a fixed structure of the toaster such as the end panel 18 (FIG. 1). In FIG. 2A, the spring 98 is connected to the top leg 92, and functions to apply a return force FR to the bread support bracket 74 biasing the bread support bracket 74 towards a top end 100 of the rod 60. The bracket 74 is shown in FIG. 2A in its OFF position before the handle 78 (FIG. 1) has been actuated downwardly to begin a heating cycle. In this position, the slide 56, which is connected to the bread support, rests on an upper surface of the bottom leg 96. The slide 56 thus maintains the bread support in its upper position.
In FIG. 2B, an external force FE is applied to the bread support bracket 74 sliding the bracket 74 bread support towards a bottom end 102 of the rod 60. As the bread support bracket 74 slides along the rod 60, the slide 56 carrying the bread support is allowed to move downwardly along the rod 60 towards the bottom end 102. The slide 56 continues to move downwardly until it contacts a stop 110, which is shown in FIG. 2B. Although a discrete stop 11 is shown in FIG. 2B, it will be understood that the stop 110 may be implemented in other ways such as limiting the downward movement of the bread support. After the slide 56 contacts the stop 110, the bracket 74 may continue to be displaced downwardly because the upper leg 92 is spaced from the lower leg 96 by a distance that is greater than the height of the slide 56. However, when the upper leg 92 of the bracket 74 contacts the slide 56 as shown in FIG. 2B, the bracket 74 has reached its lower-most position. In this position, the bracket 74 closes a switch (not shown) in the switch mechanism and retainer 82 to causing power to be applied to electronic circuitry and thereby initiating a heating cycle of the toaster 10. When power is supplied to the electronic circuitry, a coil (not shown) is energized and generates a retaining force FC that secures the bracket 74 in the position shown in FIG. 2B during the heating cycle of the toaster 10. The retaining force FC generated by the coil must be greater than the return force FR from the spring 98 in order to hold the bracket 74 at the desired position.
As shown in FIG. 2C, at the end of the heating cycle, which is determined by a timer (not shown) in the switch mechanism and retainer 82, the electromagnet removes the retaining force FC, thereby allowing the spring 98 to slide the bracket 74 upwardly along the rod 60. The lower leg 96 of the bracket 74 then contacts the slide 56 to raise the slide 56, and hence the bread support, along with the bracket 74 to the OFF position shown in FIG. 2A.
As is well known in the art, it is possible for a food item to get caught in the bread cavity 40 during a heating cycle. In such cases, the food item can prevent the bread support from being carried upwardly by the spring 98 coupled through the bracket 74. The bracket 74 and slide 56 will then be stuck in the position shown in FIG. 2C. However, even though the stuck slide 56 prevents the bracket 74 from moving upwardly to the OFF position shown in FIG. 2A, the bracket 74 is able to move from the ON position shown in FIG. 2B to the stuck position shown in FIG. 2C. The upward movement of the bracket 74 to the stuck position is sufficient to allow the bracket 74 to deactivate the switch in the switch mechanism and retainer 82. Thus, power is removed from the toaster 10 even if the slide 56 becomes jammed in its downward position. If the spacing between the top and bottom legs 92, 96, respectively, of the bracket 74 was not greater than the height of the slide 56, a stuck bread support slide 56 could hold the bracket 74 in the down position to maintain the switch in the switch mechanism and retainer 82 closed and thereby causing power to be continually applied to the toaster. In this situation, the toaster 10 could become dangerously hot.
One problem with the conventional toaster 10 is that the return force FR exerted by the spring 98 when the bread support bracket 74 is in its lowered position is relatively large. Thus, a large coil is required to generate the retaining force FC having a magnitude greater than the return force FR. A large coil is typically more expensive than a smaller coil, and thus increases the cost of the toaster. The manufacturing volumes of conventional toasters may be very large, and thus a more expensive coil in each toaster may result in the expenditure of a large sum of money. Furthermore, size constraints within a typical toaster may be rather limited and a large coil occupies valuable space. For example, the coil must typically be mounted on a printed circuit board containing the electronic circuitry that controls operation of the toaster. A large coil occupies valuable space on the printed circuit board and thereby limits the other circuitry that can be placed on the printed circuit board or increases the size and cost of the printed circuit board.
Some conventional toasters using electronic timing and control circuits use a mechanical latch to maintain the bread support in the down position during the heating cycle. The heating cycle is terminated by an electronic timing circuit driving a solenoid coil to cause the solenoid to release the latch. When the latch is released, the bread support rises and the switch is opened to remove power from the heating elements of the toaster. Unfortunately, if the timing circuit or solenoid fails for some reason, the latch will not be released, thereby indefinitely prolonging the heating cycle and potentially creating a fire hazard.
Other aspects of conventional toasters also unduly increase the manufacturing cost of such toasters. For example, the need to solder power wires to switching, timing and retainer sub-components, the relatively large size of circuit boards used in the switching and timing circuits of electronic toasters, and the assembly of components in switching, timing and retainer subcomponents all markedly increase the cost of manufacturing toasters.
There is a need for a switching, timing and retainer mechanism that reduces the magnitude of the force required to hold a bread support in a desired position during a heating cycle of the appliance, that terminates rather than prolongs the heating cycle in the event of a component failure, and that can be manufactured relatively inexpensively.
According to one aspect of the present invention, a switching mechanism for a heating appliance including a bread support adapted to support a food item to insert and remove the food item from a cooking cavity of the appliance. The appliance includes an electronic circuit that controls operation during a heating cycle. The switching mechanism includes a switch having a first terminal adapted to receive a power signal and a second terminal coupled to a component of the heating appliance. The switch operates responsive to an applied switching force to couple the first terminal to the second terminal. A switch actuator has a first end, a second end, and a retaining member spaced apart from the first end. The second end is attached to the appliance to rotate about an axis. The switch actuator operates responsive to a force being applied to the bread support to rotate about the axis to a first position and apply the switching force to the switch so power is applied to the component of the heating appliance. The retaining member engages the bread support to maintain the bread support in a lowered positioned in the cooking cavity when the actuator is in the first position. A retaining mechanism applies a retaining force to the first end of the switch actuator to secure the switch actuator in the first position responsive to power being applied to the component of the heating appliance. The retaining mechanism removes the retaining force at the end of the heating cycle to allow the switch actuator to rotate about the axis to remove the switching force and thereby remove power from the component of the heating appliance.
According to a second aspect of the present invention, a printed circuit board includes a substrate and at least one electrical contact formed on the substrate. The electrical contact is connected to electronic circuitry formed on the substrate. The electronic circuitry operates to control the operation of a heating appliance. A switch blade is provided for each electrical contact. Each of the switch blades is adapted to receive a power signal and is physically separate from the printed circuit board. Each switch blade is operable to touch the corresponding electrical contact to apply power through the contact to the electronic circuitry. According to a further aspect of the present invention, a switching mechanism for a toaster comprises a plurality of switch blades, each of the plurality of switch blades being adapted to receive a power signal and apply the power signal to a corresponding contact coupled to a component of the toaster. Each of the switch blades has a first end secured between a first mounting structure and a second mounting structure. The second mounting structure is heat-staked to the first mounting structure.
According to yet another aspect of the present invention, a switching mechanism for a toaster includes a plurality of switch blades, each of the plurality of switch blades being adapted to receive a power signal and apply the power signal to a corresponding contact coupled to a component of the toaster. Each of the switch blades includes a first end having crimp details formed at the first end. The crimp details are adapted to crimp an electrical wire that provides the corresponding power signal to the switch blade.